Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$99.33	9.332%	$108.5995	$108.60	$108.60	$108.60
Purchase #2	$163.61	3.748%	$169.7421	$169.74	$169.75	$169.70
Purchase #3	$42.59	5.789%	$45.0555	$45.06	$45.05	$45.10
Purchase #4	$176.73	3.336%	$182.6257	$182.63	$182.65	$182.60
Purchase #5	$131.76	9.491%	$144.2653	$144.27	$144.25	$144.30
Purchase #6	$206.97	12.653%	$233.1579	$233.16	$233.15	$233.20
Purchase #7	$176.67	3.335%	$182.5619	$182.56	$182.55	$182.60
7 purchase totals =	$997.66		$1,066.0079	$1,066.02	$1,066.00	$1,066.10